Politicians in Washington may not yet be convinced of the viability of renewable energy like wind power, given the Hill’s repeated delays in renewing federal tax-credits. But there are a few true believers: big European utilities convinced the U.S. is the El Dorado of wind power.

E.On, one of Europe’s biggest power companies, said Thursday it will invest the lion’s share of its renewable-energy budget in the U.S. Why is that, given that Germany is the home of fat subsidies for renewables and still the world leader in wind-power capacity? There’s no lebensraum there—wind resources are poor, and offshore wind is still more dream than reality....